a. Field of the Invention
This invention relates to implementing multicast transmission over bonded broadband. Broadband bonding refers to the aggregation of broadband channels such as multiple fixed and or/wireless channels to provide an aggregated channel with a corresponding higher bandwidth. Multicast refers to the transmission of data to a group of destination computers simultaneously in a single transmission from the source.
In this description reference is made to the OSI seven layer protocol stack summarised briefly in the table below. The terms packets and datagrams are used interchangeably in this application.
LayerNameFunction1.PhysicalA not necessarily reliable direct point-to-point dataconnection.2.Data linkA reliable direct point-to-point data connection.3.NetworkAddressing, routing and not necessarily reliabledeliveryof datagrams/packets between points on a network.4.TransportReliable delivery of datagrams/packets betweenpoints on a network.5.SessionInterhost communication, managing sessionsbetween applications6.PresentationData representation, encryption and decryption,convert machine dependent data to machineindependent data7.ApplicationNetwork process to application
b. Related Art
In multicast datagram transmission copies of datagrams/packets are automatically created in network elements, such as routers when the topology of the network requires it. Internet Protocol (IP) multicast is often employed in applications such as streaming media and Internet Protocol Television (IPTV). The implementation of the multicast concept occurs at the network layer, where routers create optimal distribution paths for streams of datagrams/packets sent to a multicast destination address.
Broadband bonding can occur at any layer, but when it occurs at the network layer or above it is not a simple matter to support multicast services. When bonding at lower level in the protocol stack, for example at the data link layer or the physical layer, it is possible to deliver multicast services over them because a bonded link appears as a single virtual connection to the network layer protocol.
However for bonding solutions above the data link layer, a multicast stream would typically be received at an aggregation server (or equivalent), and packets within the stream would be sent on a round-robin basis to an end user's routers, then aggregated at the other end, again as a multicast stream. The problem with this approach is even though a multicast stream is sent out on the customer local area network, no network layer multicast capability is utilised, essentially unicast packets are sent and no multicast efficiencies are achieved.
There is a need for a method of sending a multicast stream over bonded broadband lines without losing the efficiencies of multicast due to the bonding employed.